ABSTRACT
The importance of global vaccines for various infectious agents has been emphasized through our experience with the current COVID-19 vaccine. Physicians trained in allergy and immunology are considered experts in vaccines and adverse reactions from vaccines. This chapter will emphasize how to approach vaccines for various populations, including immunodeficient patients, how to determine best paths for patients who miss vaccine doses, and how to address adverse reactions to vaccines, as noted in Case 2, where the patient experienced an anaphylactic reaction to the measles, mumps, and rubella (MMR) vaccine. In addition, mechanisms behind adverse vaccine reactions are discussed. © The Editor(s) (if applicable) and The Author(s), under exclusive license to Springer Nature Switzerland AG 2022.